P r o m i s e
by ElementofHeart
Summary: [Dead!Ace x Pregnant!Reader x Onesided!Luffy] Seeing the little babe in his arms, knowing that it was his brother's, it made him feel like he wasn't alone anymore. He hadn't failed. He hadn't lost Ace completely. His brother's memory hadn't gone out of existence. He hadn't failed Ace.
**I hope you all like it~! ^^ Since there aren't many reader-inserts in this site, I might as well post one and add on to however many reader-inserts that on here.**

 **This one-shot was beta'd by** _ **Melancholy Chords.**_

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 **He had promised Ace to protect his only child.**

It was hard to believe, honestly.

[Name] had been pregnant during the entire war, with Ace's child. His brother's kid.

It was a wonder why she didn't show up to the battlefield, with her fighting alongside the Whitebeard Pirates—but at that moment when it was revealed to him that she was with child, it all clicked in his head.

And it hurt.

He knew he never had a chance with her from the start; she never gave him that same smile she gave Ace, the way her eyes sparkled just for him and the teasing that went between the two of them. He already knew that having these feelings for your brother's significant other was so _wrong_ , and it made him feel like garbage whenever his heart would flutter just at the sight of her. Yet he had always asked himself what Ace had that he didn't.

Was it that Ace was just hot to her? Did she like him because of his body?

The answer was already no. Because she wasn't that shallow—she had told him once that she would always get to know someone before liking them, almost like testing to see if they were right for her, and in this case; Ace had passed her test.

Was it because he was younger than her? He didn't think age made much of a difference, and she was only two years older than him. But maybe in her eyes, it was different. He would always be known as "Ace's little brother" to her.

Or maybe...it was because Ace and her had a connection that she hadn't had with him. And the thought of that hurt him. _Hard._

It definitely didn't help at all with coping about Ace's death whenever [Name] would wake up screaming his brother's name, as she woke up from a horrifying nightmare that had become reality in just a day. On those days, he would be the first one in her room, clutching her small, shaking body into his arms and holding her as if her life depended on him. And it did, from what she'd told him one night as they both laid under tufts of grass in the Amazon Lily watching as the moon shone brightly at them.

A thought that he carried with him with pride whenever he thought of the [hair color] haired pregnant woman.

Her nightmare were always about Ace leaving her and their child—with his brother walking away from them without saying goodbye. And it hurt his heart worse than the thought of Ace's death, watching her breakdown in front of him (it hurt even more knowing that her nightmares was indeed the horrible truth). She was always strong to him, always joking and laughing about anything, and just a natural ball of sunshine. She was just so... _amazing_ , that the remembrance of Ace being her first just by seeing the bulge of her stomach hit him like a train.

But he never once hated the child inside her, growing with his brother's blood. Not even when a piece of him felt guilty that he wished it was his.

The Navy still hadn't discovered that Gol D. Roger's lineage still lived on—along with his will. And for that, both [Name] and him were grateful. It meant she wouldn't have to hold her child as long as Ace's mother had with him—she wouldn't have to live in constant fear of the Navy showing up on the island to look for her child and take the offspring away from her.

Not that he'd ever let that happen. He'd make sure not a finger was dared lay on [Name], and would fight until he could not longer stand up and protect her.

But there was one thing that he knew he couldn't ever protect her from, so when it happened: he wasn't prepared.

The delivery.

"Ahh!" She cried out in pain, her face scrutinizing in concentration as her breathing became heavily labored. "T-this...this hurts...!"

He stared wide-eyed at her with concern, letting her grip tightly on his hand as he asked, "O-oi, is [Name] going to be okay?"

He'd heard about horror tales on how babies were born based on what Makino had been told in the village. While he hadn't really paid attention to it, seeing as he hadn't been interested at the time to start a family, he only caught that it was was the most painfullest experience a woman could had.

And were they right.

"Of course she is!" The Elder Nyon snapped, looking at the [hair color] haired girl's form as she let out a moan. "Anyways, you're supposed to be supporting her, Luffy. Stay focused on her."

[Name] yelled out in pain, turning her head to the side as she held on tighter to Luffy's hand, completely suffocating it. But he didn't feel a thing, instead his eyes growing worried as he began a few minutes later, "But, are you sure...?"

"You're supposed to be here to help her, not make her worry more! Show some composure!" Nyon turned to look back under at [Name], with the blanket covering her up. "This much pain would be unbearable to any man! But women are strong!"

Reluctantly, Luffy turned to [Name] once again, watching as she took a second to breathe, her eyes still shut tight. Beads of sweat began to go down his face as he clenched his teeth, thinking inwardly, 'Hang in there, [Name].' He hated to see her in such pain, and just wanted it all to end for her.

He looked at the bulge in [Name]'s stomach, silently adding, 'Hang in there, Sabo.' It was the name [Name] had said before that Ace had wanted to call him if it were a boy, Rouge if it were a girl—both named after incredible people in his life.

Even if he didn't know why, Luffy had a gut feeling that it would be a boy and began calling the unborn babe as such.

His thoughts were broken by [Name]'s suppressed screams, as she turned her head to the other side. She let out a cry of pain, her forehead beaded with sweat as her [hair color] hair was spread out everywhere on the bed.

He had never felt so helpless in his life, watching her laying in agony on that bed. He had the power to beat navy soldiers, destroy buildings, beat the strongest of foes—but even with that strength, he still couldn't have done anything to prevent that sort of pain. And only in that moment did he feel a much stronger urge to get stronger.

And then, the (almost) best news of his life was heard: "The head is out! You're almost done, [Name]!"

These words were followed by another woman from the Amazon who had been helping Nyon since the beginning of the delivery, her mouth covered by a surgical mask as she said, "Hang in there, [Name]-san!"

[Name] only continued to push, twisting her head side to side as she yelled out in pain. Luffy looked at [Name] and then back to her stomach, saying quietly, "Come on, Sabo—you're almost there."

Moments later, [Name]'s screams grew increasingly louder, as did her grip on him as she pushed as hard as she could, more so than he had ever seen in the past hours.

Nyon continued to look down at the almost-new mother, her eyes narrowing slightly for a few moments.

And then wails were heard in the room. A baby's wails.

"Hot water!" Nyon immediately commanded, with the nurse assistant gave her a quick nod and did so.

The next few moments were a blur to Luffy: he got to see the child first—Ace's child—and saw its dark tufts of hair as it was wiped clean with a cloth after they had cut the cord. It's wail never ceasing as it was wrapped in a blanket, with Nyon instructing him on how to hold it.

And when he did, it was the most odd, yet wonderful feeling in the world.

He couldn't help but stare wide-eyed at the child, the way it's eyes were shut closed as it cried out softly, not as loud and hysterical as it did before. It felt so...foreign to him. And in all honesty, at that moment, he felt afraid.

Such a small, fragile life was born. It was born into the Pirate Era, where dreams were followed and darkness lurked. Could it possibly survive in a world like that?

But only one thought clouded his mind above all that worry.

Ace's son was finally born...a piece of his brother was _in there._

And at that realization, tears began to fall from his face and onto the child's face. Luffy held onto the babe, making sure that it was warm and alive as he continued to cry in both anguish and happiness.

This...this being, this small baby was all it took to make him start bawling like a child. And he wasn't one bit ashamed of it.

"Ace...ace," he whispered to himself, closing his eyes. It was an indescribable feeling he felt; he didn't know what it was that made him so happy. Seeing the little babe in his arms, knowing that it was his brother's, it made him feel like he wasn't alone anymore. He hadn't failed. He hadn't lost Ace completely. His brother's memory hadn't gone out of existence.

 _He hadn't failed Ace._

"Hey...Luffy..." Luffy stopped for a moment, tears still falling from his cheeks as he turned to [Name], her eyes shone with both happiness and restlessness. The young woman gave a small, albeit weak smile, saying, "Can I...can I see him?"

He was right, it was a boy. Luffy hadn't honestly remembered Nyon say anything...

Luffy sniffled, giving her a huge smile that reached his eyes, saying softly, "Yeah, here he is." He walked over to the weak mother, sitting on a stool beside her as he held on to the baby properly, and let [Name] have a peek at the child.

At the sight of her son, [Name] said quietly, a small smile on her face as her eyes lit up for the first time in a long while, "So we finally meet...Sabo." Her eyes slowly began to well-up with tears as Luffy gently handed her the babe, with the child's soft wails reaching [Name]'s ears.

The young, new mother closed her eyes content, as tears fell from her cheeks. She began to say softly, "You have no idea how long I've been waiting for you...how long we've been waiting for you." At the indirect mention of his name, [Name] felt a lump in her throat, despite holding a smile. She pulled her child close to her cheek, nuzzling the rosy child as he wailed.

She said after sniffling and trying to keep composure, her eyes not once taken off her child as she continued, "Y-your daddy...he's not here with us now...but if he was, I'm sure he'd be all over you by now."

His heart felt that familiar ache, and it took all his willpower not to walk out of the room and sob quietly to himself. The wounds were still as fresh as if it were yesterday—but to hear [Name] declare it again was just too much for him to bear, almost knocking the wind out of him.

"His name was Portgas D. Ace...he was an amazing man, your daddy. H-he always wanted to meet you; he told me stories about how he'd spoil you rotten, and make sure...t-that he would always...be there for you..." [Name] bit her lip, as she desperately tried to suppress the oncoming full-on sob that was threatening to unleash. God, how she missed him. All she could think about was how Ace was supposed to be beside her, holding their child and giving her his usual smile. That reassuring smile, the one that always told her that everything was going to be just fine now that she had him near her.

She sniffled. How pathetic she was, feeling like this when she should be happy about the birth of her child.

Their child.

She took a deep breath, her head spinning and her nose stuffy as she started once more, "But you know...even if you're real daddy isn't here...there was someone your daddy said he'd choose as a substitute if..." She never finished her sentence, instead turning her attention to Luffy, watching as he was standing beside the door, strawhat shadowing his eyes.

Said rubber man immediately turned to her when she said, "Your daddy said...your oji-san Luffy would be your new daddy if something...ever happened to him."

If there was any moment that Luffy was ever caught of guard, this would probably be the most biggest moment in his life.

Him? The father to Ace's son...?

Ace said that?

As if reading his mind, the young woman gave the first genuine laugh she had in a while, "Ace said that, you know. The first weeks of my pregnancy, he just...randomly told me, and he promised me to accept his will..."

She looked at him with soft, ready [eye color] eyes that almost made him melt right on the spot. The same guilty feelings for her that he had kept hidden all this time had returned, this time overflowing, and he had no idea how to stop it. "And of course, I said yes."

For the first time in his entire, Luffy was thinking about something.

"Ace...said that...?" He said, more so to himself. He imagined Ace saying that with his usual smile on his face, the way his smile could grow just as large as his, and for a fleeting moment, Luffy could faintly hear the whisper of his dead brother telling him eagerly to assume the responsibility. And in that moment he had never felt more honored in his life to accept something was worthy as "father", and in an instant he agreed to it.

The look on [Name]'s face when he accepted that role...he knew he would remember it until his last breath.

As night fell on the Amazon Lily, he was allowed permission to stay in the same room with [Name] and the newborn Sabo. Not that he ever noticed Hancock's jealous fury towards the previously pregnant women, he was still clueless to her (obvious) attraction on him.

He was currently still awake, lying next to the window as the moon's ray gave some light into the otherwise dark room. A sense of purpose washed over him, and he couldn't help but feel the tiniest corners of his lips turn upwards, as he looked up at the moon, a huge weight now lifted off his shoulders that he never knew existed.

 **And he was going to keep that promise.**

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 _"Luffy..." The strawhat boy was too in shock to say anything, his body was numb and his brain was trying progress the fact that his brother was dying right in his arms. The stench of blood began to fill his nostrils, the nausea suddenly kicking in, but all he could feel was the tears falling down his cheeks and the way his brother's body was growing cold._

 _The older male held on to his younger brother tightly, ignoring the fact that the pain was slowly starting to numb away. He had to at least do this, otherwise he couldn't be able to pass on. Ace said moments later with a smile near the end, tears escaping his eyes at the thought that he wasn't coming back home to the girl he loved, nor would he be able to see his own child be brought into the world._ _But he didn't regret anything. He didn't regret loving you, or his unborn child._

 _With the rest of the words he could muster, he said quietly, "...promise me that you'll protect [Name] and my kid, okay? I know she'll kill me for this...but I want you to know, I'm counting on you."_

 _Luffy could only nod numbly, unaware of better the future to come._

 _"I...promise."_


End file.
